Exercise-induced ST-segment elevation in leads over infarcted area and residual myocardial ischemia in patients with previous myocardial infarction.

The purpose of this study was to evaluate the clinical significance of exercise-induced ST elevation in patients who had previous myocardial infarction. Electrocardiographic leads were placed over the infarcted area in 65 patients who had previous myocardial infarction (PMI; isolated left anterior descending coronary artery disease). All patients also had stress thallium scan. Exercise-induced ST changes in leads placed over patients' infarcted areas were compared with the extent of both their myocardial ischemia [thallium ischemic score (TIS)] and the area of their infarcted tissue [defect score (DS)]. The latter was derived from a circumferential profile analysis. In patients who had PMI less than three months after the onset of myocardial infarction (n = 36), the left ventricular ejection fraction (LVEF) and the extent of abnormal left ventricular wall motion did not significantly differ from those in patients with exercise-induced ST elevation (greater than 2 mm, n = 26; less than 2 mm, n = 10). In patients who had PMI more than three months after the onset of myocardial infarction (n = 29), patients with high exercise-induced ST elevation (greater than 2 mm, n = 15) showed left ventricular dyskinesis more frequently than those with low ST elevations (less than 2 mm, n = 14). In addition, the former showed higher DS and lower TIS than the latter. In patients who had PMI less than three months after onset (n = 26), 73% of those with ST elevations with prominent upright T waves (n = 15) also had transient thallium defects in their infarcted areas. They also had higher LVEF and TIS than those with low ST elevations (less than 2 mm, n = 11). These results indicated that exercise-induced ST elevations in leads placed over the infarcted areas are to be interpreted differently depending on the degree of recovery of injured myocardial tissue.(ABSTRACT TRUNCATED AT 250 WORDS)